6L6 Tube Review
I've been experimenting for years working to find the right mix of good sounding and reliable 6L6 tubes to stock here at the shop. After installing thousands of tubes, here are my three top picks and why.
Top Pick – Tung-Sol 6L6GC STR. This tube has only been around a few years. It's built by the same factory that makes the Sovtek and Electro-Harmonix tubes but the Tung-Sol tubes from this factory are generally built a little more solidly that the other brands they offer. The glass is thick and the plates are welded. The entire guts of the tube are suspended by “springs” to reduce vibration and microphonics. The tone is well balanced with a strong bottom end. The overall volume and clean headroom is very slightly lower than since the tube breaks up just a bit earlier in the volume range. The breakup (clipping) is very smooth in this tube. It's a good choice when you want to tame a harsh sounding amp or if a little less volume is desired before distortion.
Second Pick – Sovtek 5881WXT. This Russian tube is not a true 6L6 or 5881 but a rugged design made for military use. This one comes standard in many new amps and is sometimes seen with a Fender or Groove Tube label. The tone is not outstanding but it mates well with some amps, especially overly bright-sounding amps. Treble content is somewhat reduced and lacking in harmonics. There is ample bass but it can tend to get a little loose and flabby in the bottom when pushed, especially as the tube gets old. The tube sounds reasonably good, it's very reliable (even in high voltage amps) and the price makes it a good value. The maximum plate dissipation is only 22.5 watts so bias must be adjusted for lower idle current than a Standard 6L6GC.
There are several other good sounding 6L6 tubes available such as the JJ 6L6GC from the Slovak Republic and the TAD and Valve Art and Ruby from China but because of consistent quality problems or cost to quality ratio, I have not been stocking them.